What Is the R Value for a Hollow Metal Door?

When shopping for commercial doors or windows, you may see references to anR value. This specification is especially important forexterior hollow metal doors where energy efficiency and thermal performance matter.

Below, we explain what the R value means, why it matters, and what affects the R value of a hollow metal door.

What Does R Value Mean?

The R value measures how well a door resists the transfer of heat. A simple way to remember this is that the “R” stands for resistance.

As a general rule:

• Higher R value = better resistance to heat transfer
• Lower R value = less resistance to heat transfer

A hollow metal door with a higher R value is more effective at keeping heat out during hot weather and keeping heat in during cold weather.

Why Is the R Value Important for Hollow Metal Doors?

R value plays a significant role in overall building energy performance, especially when the door is part of the building envelope.

Commercial buildings rely on multiple components to control heat transfer, including insulation, roofing systems, wall assemblies, windows, and doors. If a door has a low R value, it can become a weak point that allows heat to move in or out of the building.

In practical terms:

• In summer, higher R values help keep hot exterior air out
• In winter, higher R values help retain interior heat

For this reason, a higher R value typically indicates that a hollow metal door is suitable for exterior applications or areas where thermal efficiency is important.

Factors That Affect R Value in Hollow Metal Doors

Door Thickness

Door thickness is one factor that influences R value. In general, thicker doors provide better resistance to heat transfer.

Most commercial hollow metal doors are:

• 1-3/4" thick - standard commercial thickness
• 1-3/8" thick - lighter-duty applications

A 1-3/4" thick hollow metal door will typically have a higher R value than a 1-3/8" thick door with the same core type.

Core Type

The most significant factor affecting R value is the door core. Although they are called “hollow” metal doors, all commercial hollow metal doors contain an insulated core.

The two most common core types used in the vast majority of installations are:

• Polystyrene foam core
• Honeycomb cardboard core

Polystyrene Core vs Honeycomb Core

Polystyrene core hollow metal doors offer higher thermal performance than honeycomb core doors.

• Polystyrene core R value: approximately 2.4 to 2.8
• Honeycomb core R value: approximately 1.7 to 1.9

Because of the higher R value, polystyrene core doors are commonly used for both interior and exterior applications. Honeycomb core doors are most often used for interior commercial openings where insulation performance is less critical.

Glass and Vision Lites

Vision lites (glass windows) can also affect the R value of a hollow metal door. The amount of glass and the type of glazing used will influence overall thermal performance.

Larger glass areas and non-insulated glazing typically lower the overall R value of the door assembly.

Conclusion

The R value of a hollow metal door depends on several factors, with core typeand door thickness being the most significant.

If you need a hollow metal door with strong thermal performance, doors with apolystyrene core provide better resistance to heat transfer and are well suited for exterior applications.

To explore energy-efficient commercial steel doors or configure a custom opening, browse ourCommercial Hollow Metal Doorsor use ourBuild Your Door Quote Tool.

Need help choosing the right door? Call 866-232-5673 or text photos to 210-275-8966 for expert guidance.